The natural gas investment tax rate for any taxable year shall be determined on the basis of the internal rate of return on the cumulative annual cash flows of the taxpayer derived from natural gas investment activities, which applies to the subsequent year . The applicable tax rate is progressive, starting at 30 percent for an internal rate of 8 percent or less, and reaching 85 percent for an internal rate of 20 percent or higher.

The annual cash flows shall be calculated by adding back any operational losses carried from previous years, non-cash items deducted for the purpose of determining the taxpayer's natural gas investment tax basis and all financing fees and any other bank service fees, and subtracting capitalized cash expenditures and the natural gas investment tax and the corporate income tax actually paid to the Kingdom for the financial year.